Numerous folding truss-structure systems exist. Most of these allow for either trusses with no curvature, or single curvature (i.e. cylindrical). Those that are specifically addressed to double curvature, are in general limited to spherical geometries and are complex in operation and construction. None allow for more varied geometries, such as toruses, ellipsoids, helical surfaces, faceted polyhedra and irregular three dimensional geometries.
I have discovered a method for constructing reversibly expandible truss-structures that provides for an extremely wide variety of geometries. Trusses formed by this method will collapse and expand in a controlled, smooth and synchronized manner. Such structures require no complex joints. Connections are limited to simple pivots.
A significant characteristic of previous systems for folding truss-structures of curved geometry is that the overall shape of the truss changes during the folding process. Thus, a spherical or cylindrical shape will tend to flatten as the truss is folded, or change is some other manner. As the overall shape changes, a high level of complexity is introduced into the relations between truss elements during folding. This will in general lead to:
a. Bending and distortion of truss elements during folding. The result of this bending is the existence of `hard points` in the folding process where forces must be overcome to open or close the structure. Thus the truss must be constructed from flexible materials, which is not desired for most structures.
b. Requiring complex joints with more than one degree of freedom, such as sliding joints, ball joints, etc. These connections are more expensive to manufacture than simple pivot connections and not as structurally sound.
c. The structure tends to be weak or `floppy` when in a partially folded condition. The reason is that the favorable structural characteristics that are possessed by the truss largely come from its overall geometry. Since that geometry changes during the folding process, it tends to pass through configurations that are not structurally sound.
d. Severe limitations exist on the types of overall shapes that such systems can handle. Since even relatively simple shapes (such as a sphere) introduce high degrees of complexity, more complex geometries become impracticable.
Thus, it is an object of the present invention to provide a three-dimensional folding truss whose overall shape and geometry is constant and unchanging during the entire folding process. The reasons are the converse of the above:
e. Rigid materials may be employed, and a smooth effortless deployment process occurs.
f. All joints are simple pivots which are simple, compact, structurally favorable and inexpensive.
g. The structure retains its structural soundness during folding or unfolding. All movement in the structure is the actual deployment process, not floppiness.
h. A virtually unlimited range of geometries may be handled.
The net result of these characteristics is a system that allows for a wide range of possible uses, ranging from tents, pavilions, gazebos and the like to novelty items, entertainment decor, etc. to folding furniture, partitions and home furnishings.
Due to the combination of structural integrity and smooth deployment, large structures are practicable and may be deployed automatically if desired. Such applications may include stadium covers, temporary industrial warehouses, and temporary housing or shelters.